The present embodiments relate to silicone surfactants for use in polyurethane foams. More particularly, the present embodiments relate to silicone surfactants having dimethyl siloxane backbones with attached alkyl and polyether pendant groups that provide improved properties for flexible urethane foam compositions utilizing vegetable oil based polyols.
Polyurethane foams are extensively used in a variety of industrial and consumer applications. The general production of polyurethane foams is well known to those skilled in the art. Polyurethanes are produced from the reaction of isocyanate groups present in polyisocyanates with hydroxyl groups present in polyols. The polyurethane foam production, the reaction of polyisocyanates with polyols, is carried out in the presence of several additives: surfactants, catalysts, cross-linking agents, flame retardants, water, blowing agents, and other additives. Surfactants are typically necessary during the polyurethane foam manufacturing process, and have a significant impact on the final polyurethane foam physical properties. Most conventional type surfactants are based on siloxane/polyether copolymers. Flexible polyurethane foams, a subcategory of the polyurethane foams, are generally soft, less dense, pliable, and subject to structural rebound subsequent to loading.
Polyols used in the production of polyurethanes are typically petrochemical in origin, being generally derived from propylene oxide, ethylene oxide and various starters such as propylene glycol, glycerin, sucrose and sorbitol. Polyether polyols are the most common polyols used in polyurethane production. For flexible foams, polyether polyols with molecular weights of from about 2,000 to 10,000 are generally used. These type of polyols contribute to the depletion of petroleum-derived oil, a non-renewable resource.
Thus, in recent years, vegetable oils based polyols have penetrated a variety of polyurethane applications. Growing consumer demand for “greener” products and the depletion of non-renewable resources have created increasing demand for polyurethane foams produced with renewable content. Derived from renewable resources, vegetable oils based polyols, also known as “natural oil based polyols” (NOP), present an alternative to petroleum-based feedstock. As both polyols suppliers and polyurethane foam producers have recognized this opportunity, NOP are increasingly used in a broad range of polyurethane foams, in combination with petroleum based polyols.
NOP currently used in polyurethane foams are usually based on at least one vegetable oil, including but not limited to soybean, castor, sunflower, canola, linseed, cottonseed, tung, palm, poppy seed, corn and peanut. In one respect, NOP may generally be categorized as hydroxylated vegetable oils or alkoxylated vegetable oils, depending on the extent and the nature of the chemical modifications the vegetable oils are subjected to. These are commercially available from various manufacturers.
The use of petroleum-based polyols in polyurethane foams is a well-established technology that has created products with strict industry requirements. Thus, the attempt to partially or totally substitute them with NOP in the manufacturing of polyurethane foams, has resulted in loss of product quality. This is especially true in the case of flexible polyurethane foams, where increasing incorporation of NOP has a negative impact on the physical properties of the foam.
Nevertheless, because the benefits of using NOP in the production of polyurethanes, particularly from an environmental standpoint, efforts are being made to continue to use them. Thus, solutions to mitigate the negative impact on physical properties resulting from the use of such polyols have been provided mainly by the producers/suppliers of the NOP, and are related to incorporating additional polyol components in the foam formulation (US Patent Publication No. 2006/0235100) or structural modifications of the vegetable oils based polyols (US Patent Publication No. 2007/0238798).
The present invention works to minimize or eliminate the loss of foam physical properties in flexible polyurethane foam formulations manufactured using NOP by using a specific surfactant composition. There are no previous solutions to the physical property issues encountered when using NOP in urethane foams that address the problem by using modified structure siloxane/polyether/alkyl surfactants, the subject of the present invention.
For comparison purposes, U.S. Pat. No. 6,653,359 describes a conventional siloxane/polyether surfactant. The use of these prior types of surfactants in flexible polyurethane foam formulations using vegetable oils based polyols results in degraded physical properties for the foam. In contrast, the siloxane/polyether/alkyl surfactants presented in this invention provide improved foam physical properties for the foam compared to prior art surfactants, enabling increased use levels of NOP into the flexible polyurethane foam formulations.